Modeling benefits of vaginal microbicides

Rachel Tompa

While a completely effective method to prevent HIV infection remains elusive, vaginal microbicide gels have shown promise of reducing HIV acquisition in women in recent studies. These gels could be an especially important prevention tool in some parts of the developing world, where the burden of HIV falls disproportionately on women, and it may be difficult for women to negotiate condom use. In parts of Africa, 61 percent of HIV infected people are women. Aside from the immediate benefit to women, some researchers postulate that the gels could benefit men, as they have the potential to reduce infectiousness of HIV positive women, although this has not been tested. Conversely, since some of the gels share ingredients with anti-retroviral therapy treatment, it is also thought that continued microbicide use in HIV positive women might lead to increased incidences of infection with ART-resistant strains of HIV. These two scenarios are possible, since many people in the developing world don’t know their HIV status.

To address the possible total benefits to men and women from an effective vaginal microbicide gel, VIDD staff scientist Dr. Dobromir Dimitrov and colleagues, including VIDD affiliate investigator Dr. Benoit Masse, developed a mathematical model to study the potential effects of the gel on a heterosexual population in the developing world. Modeling 63 different scenarios based on various possible effects of the gel, treatment schedules and ART use, the researchers found that overall, the gel is most likely to be of primary benefit to women. If a microbicide gel is made available for public use, the researchers’ models will be of value to interpret its effects on HIV transmission to men and infection with ART-resistant strains.